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研究報告

更新日期: 2015-02-09
點閱數: 1,702

三大洋劍旗魚、旗魚類及南方黑鮪生物暨資源評估

年度 2013
計劃名稱 三大洋劍旗魚、旗魚類及南方黑鮪生物暨資源評估
中文摘要 「三大洋劍旗魚、旗魚類及南方黑鮪生物暨資源評估」之中文摘要: 一、「太平洋黑皮旗魚及北太平洋與大西洋劍旗魚CPUE標準化暨資源研究」        本研究彙整1967-2011年太平洋以及大西洋台灣鮪釣漁業資料,利用泛線性模式(generalized linear model)以及泛加成模式(generalized additive model)標準化太平洋黑皮旗魚以及北太平洋與南北大西洋劍旗魚CPUE,分析我國遠洋鮪釣漁業旗魚類資源豐度指標變動趨勢。結果顯示模式考慮因子包括年、月、經緯度與交感效應皆為顯著(P < 0.05),太平洋黑皮旗魚CPUE在2000年後有上升趨勢,但2005年後略微下降,近兩年CPUE維持相對穩定;北太平洋劍旗魚CPUE在2002-2005年呈現下降趨勢,但2005年後CPUE呈現上升趨勢;南北大西洋劍旗魚標準化 CPUE在1990年代呈現下降趨勢,但2000年後相對穩定且近兩年有略微上升的趨勢;考慮每筐鉤數資訊僅略微影響台灣鮪釣旗魚類CPUE標準化的結果。本研究利用年齡結構生產量模式評估太平洋黑皮旗魚以及南大西洋劍旗魚資源現況,結果顯示太平洋黑皮旗魚資源已接近完全開發程度(S/SMSY = 1.00),且目前漁獲死亡率高於維持最大可持續漁獲量(MSY)水準(F/FMSY = 1.22),顯示此資源處於過漁中(overfishing);南大西洋劍旗魚評估結果顯示,目前產卵親魚量低於MSY水準(S/SMSY = 0.89),但目前漁獲死亡率已低於MSY水準(F/FMSY = 0.79),顯示南大西洋劍旗魚資源雖已過漁(overfished),但未遭受過漁中(not overfishing)。本研究評估結果建議應持續注意此兩資源的變動趨勢。 二、「印度洋旗魚類以及南方黑鮪資源研究」            本研究之目的在於進行印度洋紅肉旗魚與黑皮旗魚之CPUE標準化分析以及資源評估之分析,紅肉旗魚之標準化CPUE自1980年代開始則呈現大幅減少的趨勢,而黑皮旗魚之標準化CPUE皆顯示自1980年代中期開始減少,雖然1990年代呈現增加趨勢,但隨後又逐年減少,近年來則為大幅增加。根據評估結果皆指出目前(2011年)印度洋紅旗魚之漁獲死亡率已出皆高於MSY水準,而生物量評估結果也低於MSY水準,因此印度洋紅肉旗魚的資源現況相當不理想,在黑皮旗魚方面,資源評估結果指出目前(2011年)並未顯示印度洋黑皮旗魚資源狀態已處於過漁現象。然而,採用不同之CPUE序列其資源評估結果具有相當大的差異,因此目前之資源評估結果可能存在高度的不確定性。 此外,本研究亦採用台灣南方黑鮪之兩大漁區及CCSBT統計漁區所進行南方黑鮪之CPUE標準化分析。根據CCSBT統計漁區之結果顯示,不同漁區之CPUE變動趨勢差異甚大。然而,台灣之漁船作業分布與漁獲分布趨勢會被CCSBT統計漁區劃分為多個區塊,因此CCSBT統計漁區可能並不適用於進行台灣南方黑鮪漁獲資料之分析,未來應再根據各漁業國之漁獲特性,重新分析及義統計漁區。 三、「南方黑鮪及太平洋黑鮪之年齡成長與其生態研究」        本研究計畫訓練科學觀察員於台灣延繩釣漁船上採集南方黑鮪(Thunnus maccoyii)的耳石,並且判讀南方黑鮪耳石年齡與太平洋黑鮪(Thunnus orientalis)耳石年輪。觀察員在2012年於中印度洋採集33顆南方黑鮪魚頭,經由年齡查定後,其年齡範圍為1-4歲,平均年齡1.9 ± 0.7歲,另外有一批於2007年採集於中印度洋的南方黑鮪耳石,經年齡查定,其年齡範圍為2-5歲,平均年齡3.4 ± 0.9歲。2012年觀察員於國內港口採集到168尾太平洋黑鮪耳石,其平均年齡為15.5 ± 3.9歲(6-26歲)。比較歷年(2002-2013年)觀察員所量測的太平洋黑鮪尾叉長,發現魚體的平均長度由210 cm逐年遞增到230 cm,所估算的平均年齡也由11歲逐漸遞增到17歲,造成此現象的可能的原因於內文有詳細討論,由未成熟的幼魚入添減少可能是最主要原因。 四、「太平洋主要旗魚類資源指標變動與環境因子關係研究」       本研究以加入環境因子的GAM模型,分析2001-2011台灣鮪延繩釣漁獲資料,進行太平洋劍旗魚和紅肉旗魚CPUE標準化分析,探討劍旗魚和紅肉旗魚CPUE變動與環境因子的關係。影響北太平洋劍旗魚CPUE變動的環境因子有海水面高度異常、南北向風速、SST、南方震盪指數、太平洋年代震盪指數和東西向風速;南太平洋劍旗魚部分則是葉綠素濃度、SST、海水面高度異常和風速。影響北太平洋紅肉旗魚CPUE變動的環境因子有南北向風速、SST、太平洋年代震盪指數和南方震盪指數;南太平洋紅肉旗魚部分則是SST、葉綠素濃度、南方震盪指數、海水面高度異常和南北向風速。其中環境因子的變動受到南方震盪和太平洋年代震盪的影響,在太平洋年代震盪指數為正值,對應於南方震盪指數是負值時,劍旗魚和紅肉旗魚的CPUE較高。
英文摘要 Abstract of \"Stock assessments and biological studies for swordfish, billfishes, and southern bluefin tuna in the three Oceans\": 1. \"Studies on CPUE standardization and stock status for Pacific blue marlin and North Pacific and Atlantic swordfish\" :       Fishery data and catch information of the Taiwanese longline fleets in the Pacific and generalized additive model (GAM) to examine the trends of relative abundance index. All the effects considered in the CPUE standardization including year, month, latitude, longitude, and the interactions were statistically significant (P < 0.05). Standardized CPUEs of the Pacific blue marlin showed an increasing trend since 2000, but decreased slightly from 2005 and relatively stabilized in recent two years. The standardized CPUE of North Pacific swordfish decreased during 2002-2005, but increased since 2005. In both the South and North Atlantic Oceans, the standardized CPUE of swordfish sharply dropped in the late 1990s, and then stabilized from 2000 with higher values appeared in recent two years. The results were insensitive to the inclusion of gear configuration as explanatory variables in the model for all analyses of CPUE standardizations. The stock status of Pacific blue marlin and South Atlantic swordfish were assessed using an age-structured production model (ASPM). Results show that the status of Pacific blue marlin was fully exploited (S/SMSY = 1.00) and currently slightly overfishing (F/FMSY = 1.22). The swordfish in the South Atlantic Ocean was assessed to be overfished (S/SMSY = 0.89), but not overfishing (F/FMSY = 0.79). Assessment results for both species in this study suggest that these two stocks should be monitored closely. 2. \"Studies on stock status for billfishes in the Indian Ocean and southern bluefin tuna\" :        The objective of this study is to carry out the CPUE standardizations and preliminary stock assessments for striped marlin and blue marlin in the Indian Ocean. Standardized CPUEs of striped marlin reveals substantial decline since 1980. Standardized CPUE of blue marlin deceased since mid-1980s, revealed increasing trends during 1990s but they gradually decreased for recent years. Based on the results of stock assessments, the stock status of striped marlin might be very pessimistic, current (2011) fishing mortality might be higher than MSY level and current biomass might be lower than MSY level. The stock status of blue marlin might be relatively optimistic. However, different CPUE series might result in significantly diverse assessment results and thus current assessment results are very uncertain. In addition, this study also carried out CPUE standardization for southern bluefin tuna. The CPUE standardization is performed based on the sub-area effect of either CCSBT statistical areas or Taiwanese SBT fishing ground. Standardized CPUEs generally reveal quite different trends for different area. It is apparent that the CCSBT statistical areas are not appropriate for Taiwanese SBT fleet since the main fishing grounds are separated into several parts by CCSBT statistical areas. It would be helpful to redefine CCSBT statistical areas for Taiwanese SBT fishery according to the temporal and spatial analysis of its fishing characters. 3. \"Age, growth and ecological research of southern bluefin tuna and Pacific bluefin tuna\" :      In this project, we trained scientific observers to collect otoliths of southern bluefin tuna (SBT, Thunnus maccoyii) on Taiwanese longline vessels in the Indian Ocean. The otoliths collected from SBT and Pacific bluefin tuna (PBT, Thunnus orientalis) were used for age estimation. In 2012, 33 SBT heads were collected in the central Indian Ocean and otoliths were removed in the lab. The estimated mean ages were 1.9 ± 0.7 years (range: 1-4 year). Another batch of SBT otolith were collected in the central Indian Ocean 2007 and these samples were aged this year. The mean age of year 2007 samples was 3.4 ± 0.9 years with a range from 2-5 years. The observers also collected otoliths from 168 PBT landed in domestic harbors. The estimated mean age for these PBT was 15.5 ± 3.9 years (rang: 6-26 years). The historical length data of the landed PBT measured by the observers showed gradually increasing from approximately 210 cm at year 2002 to 230 cm in recent years (2010-2013). The estimated mean age of the landed PBT also gradually increase from approximately 11 to 17 years. The decreasing recruitment of the immature PBT might be the main reason that cause the increasing trend of mean size and age of PBT landed in Taiwan although other possibilities were carefully discussed in this report. 4. \"Environmental effects on billfish CPUE in the Pacific\" :       The catch and effort data of swordfish and striped marlin for the Taiwanese tuna longline fishery in the Pacific Ocean were collected for 2001-2011. GAMs with environmental factors included are applied to standardize the CPUEs of swordfish and striped marlin. For swordfish, The GAMs results showed that sea level anomalies, meridional wind speed, SST, SOI, PDO index and zonal wind speed were important factors in explaining the variance in CPUE in the North Pacific, and chlorophyll a concentration, SST, sea level anomalies and wind speed were important in the South Pacific. For striped marlin, meridional wind speed, SST, PDO index and SOI were important factors in explaining the variance in CPUE in the North Pacific, and SST, chlorophyll a concentration, SOI, sea level anomalies and meridional wind speed were important in the South Pacific. These environmental factors related to ENSO and PDO revealed that swordfish and striped marlin are in a higher CPUE level as PDO index positive and SOI negative.
計畫編號 102農科-11.1.1-漁-F3(Z)
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